Dallas' Wade Phillips, Chicago's Lovie Smith and New York's Rex Ryan will each act as head coach/defensive play-caller.

What do Wade Phillips, Lovie Smith and Rex Ryan all have in common? They are a trio of coaches set to start a new trend in the NFL this season: Head coaches acting as defensive play-callers.

Wade Phillips started the movement when he took over play-calling duties from then-defensive coordinator Brian Stewart in the middle of the Cowboys' season in '08, and he eventually transformed the underachieving unit into a top-10 defense by season's end.

Phillips, who previously held the title of defensive coordinator for the Saints, Eagles, Broncos, Bills, Falcons and Chargers, had always been involved in the building of the defensive game plan, but he generally only offered up suggestions on play calls throughout the course of the game. However, at Jerry Jones' urging, Phillips took over control of the defense, and the team responded well under his direction.

Fueled by Phillips' success and their own desire to put their imprint on their respective defenses, Smith and Ryan have decided to act as their own defensive play-callers this season.

Smith, who spent three seasons directing a Rams defense that finished third in total defense in 2001 and led the league in takeaways in 2003, has decided to take over the Bears' defense after watching the unit drop to 21st in total defense last season. Although last year's defensive coordinator, Bob Babich, will stay on as defensive coordinator/linebackers coach, Smith will be making all of the defensive play-calling on game day and embracing the challenge of becoming a rare head coach/defensive play-caller.

"There are a lot of offensive coaches in the league that call plays, that do a little bit more on their side of the ball where their expertise is," Smith said earlier in the offseason. "For some reason, a lot of defensive coaches haven't done it. But I think it's time to change some of that."

Rex Ryan comes to New York with impeccable credentials as a defensive coordinator after guiding the Ravens to three top-five finishes in total defense during his four-year stint as their defensive coordinator. The defensive mastermind is coming off a season in which his unit led the league in takeaways and surrendered the third fewest points in the league. With his defenses enjoying so much success, it only makes sense for Ryan to continue to be the point man for the Jets' defense on game day.

Whereas the league has seen numerous offensive-minded coaches juggle play-calling duties while overseeing the team, coaches from defensive backgrounds have eschewed the practice despite earning their appointment based on their success as coordinators.

Marvin Lewis is a terrific example of an exceptional defensive coach shunning the opportunity to direct his own defense. Lewis, who directed a Ravens defense that set an NFL record for fewest points allowed in a 16-game season in 2000, has never taken over the reins of the Bengals' defense despite repeated struggles on that side of the ball. In Lewis' six-year tenure, the Bengals have never ranked in the top 10 in total defense (the defense ranked 12th last season under the direction of Mike Zimmer) and has cycled through three defensive coordinators (Leslie Frazier, Chuck Breshnahan and Zimmer).

While this is not a knock on Lewis' unwillingness to take a more active role in the defense, it is interesting that the former defensive guru didn't put the weight of the defense's success on his shoulders. Head coaches are often hired based on their reputation as coordinators, but few defensive coaches really tap into their expertise while serving as the head coach.

Conversely, offensive-minded head coaches have often preferred to direct the offense on game day despite the endless responsibilities that fall on the head coach on Sundays. Bill Walsh, Mike Shanahan, Dan Reeves and Mike Holmgren are a few of the legendary coaches who took on the responsibility of calling their own offensive plays during games, and their success in the dual role has led to others attempting to pull off the double duty.

Last season, 10 head coaches served as de facto offensive coordinators, and that number will continue to grow with new head coaches such as Josh McDaniels and Tom Cable poised to call plays for their teams in 2009.

However, this season they will face a few defensive gurus willing to engage in the chess match on game day. Although Phillips, Smith and Ryan will rely heavily on the contributions of others during the preparation phase throughout the week, they will ultimately get a chance to demonstrate the skills that led to their high-profile jobs.

With owners and fellow coaches always looking to identify the latest trends, the success of these three defensive masterminds in their dual roles could lead to more former defensive coordinators grabbing the call sheet on Sundays.